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I think we're talking past each other, or I'm not explaining it well - so I've put it in a picture so it's clearer. Completely disregard the broken side of the rocker assembly, it's damaged so that may explain why the lobe is dry. Bare in mind every other rocker across the whole engine is showing perfect oiling as expected.
211006


Why is there no oil reaching the intact intake cam lobe (Red arrow - no oil why)?

I suggest the internal intake side oilways of your broken assembly have been incorrectly manufactured and reduced or zero oil was reaching the follower. I suggest it's been that way from the factory and the lack of oil or cooling from the oil has resulted in the failure of the follower. It took a while as oil was splashing about when the engine was running, but it finally broke.

If you still have the original follower assembly, a quick inspection or a test by pumping oil into it would determine if my suggestions are correct.

Just to be clear - in no way am I criticising the owner, workshop, methods or results of the repair. That engine will now be perfectly fine. I'm only suggesting a possible cause of the initial failure which could be identified and may provide a path to compensation for the owner.
 
2012 MP4-12C
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Discussion Starter · #43 ·
I think we're talking past each other, or I'm not explaining it well - so I've put it in a picture so it's clearer. Completely disregard the broken side of the rocker assembly, it's damaged so that may explain why the lobe is dry. Bear in mind every other rocker across the whole engine is showing perfect oiling as expected.
View attachment 211006

Why is there no oil reaching the intact intake cam lobe (Red arrow - no oil why)?

I suggest the internal intake side oilways of your broken assembly have been incorrectly manufactured and reduced or zero oil was reaching the follower. I suggest it's been that way from the factory and the lack of oil or cooling from the oil has resulted in the failure of the follower. It took a while as oil was splashing about when the engine was running, but it finally broke.

If you still have the original follower assembly, a quick inspection or a test by pumping oil into it would determine if my suggestions are correct.

Just to be clear - in no way am I criticising the owner, workshop, methods or results of the repair. That engine will now be perfectly fine. I'm only suggesting a possible cause of the initial failure which could be identified and may provide a path to compensation for the owner.
That's what I've been trying to explain this whole time. Whether you see it or not, there WAS oil on it. Maybe it's the angle of the lobe with that lighting as it's not particularly apparent but I assure you there was oil on it. We addressed the fact that there was less oil than seen on the other ones and looked at the other side, which also had unequal oiling. I believe this to be because of a lack of oil still in the engine.
 

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“I’m a Tuner”
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I especially appreciate the level of interest in detailed scrutiny as to the root cause of the failure from all forum members! Sometimes more eyes are better than just a few.

I will say that off-camera we were able to observe identical oiling patterns after the repair versus the other camshaft lobes.

I do realize that the edited video may have left the viewer with less information than we had. I’m sure everyone realizes it’s hard to take 40+ hours of reality and compress it into about 45 minutes a video.

thanks again to everyone for being so involved and interested in this. It’s very rare that anyone in the McLaren community is willing to highlight publish and celebrate and debate something that’s usually considered a catastrophic event and is not typically spoken about with other owners for fear of labeling one specific car is not being perfect (or tarnishing its history or value)

Cheers

Kevin P
Supercar Garage
Kennesaw,GA
 

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Somewhere near the beginning of the video it was mentioned that the transmission and engine were going to be separated. It does not look like this happened, why?
 

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That was a mis understanding of the videographer vs. the technicians. Sorry for the verbal “typo”.... 🤓
 

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I was the main Tecnician, and I accidentally swapped Sean and Eddies name twice in the video. My bad as well!
 
2012 MP4-12C
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Discussion Starter · #48 ·
Somewhere near the beginning of the video it was mentioned that the transmission and engine were going to be separated. It does not look like this happened, why?
Prior to getting it out I was under the assumption they would need to be separated to get to some things, which wasn't the case ultimately. I've never taken a McLaren engine out or apart prior to this.
 

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If it had been me, I would have done it to replace rear main seal and front trans seal.
 

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Its a tough call, this isn't the first time this has happened either. Its worrying, it looks to me and other well known mechanics such as Thorney that it is an oil starvation issue, if the rockers were weak, they would all be braking far more often, so something there has accelerating the wear, weakening the part at its weakest point, and then basically snapped, this has been documented before on cylinder 8, so a different location to the failed OP. I have also discussed with a friend at McLaren development and he has not seen a failure himself before.

My bet is low oil, previous cold high rpm as the OP hasn't owned this car from new, it could have been a previous owner who caused the damage, we just don't know. All we can do is maintain and trust the engine as in the main they are strong.

He is a very bright guy so it wouldnt have been him. im betting previous owner mistreated when cold/ran it low on oil.
 

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thanks again to everyone for being so involved and interested in this. It’s very rare that anyone in the McLaren community is willing to highlight publish and celebrate and debate something that’s usually considered a catastrophic event and is not typically spoken about with other owners for fear of labeling one specific car is not being perfect (or tarnishing its history or value)

Cheers

Kevin P
Supercar Garage
Kennesaw,GA
I've put about 1,000 low RPM highway miles on the car now. Not a single error code. Car runs very well. Will check fluids again today but so far so good.
211029
 

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That is great news - much better outcome than a total engine replacement. The more we can collectively develop independent knowledge / expertise about these cars, the more attractive these cars will become. Dealer horror stories scare buyers away.
 

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Good to hear all is well. I think we can really conclude this as an oil starvation issue. There isn't really anything else to nail it.

weak cast - Unlikely
Cam phaser cause - very unlikely
seen high loads while cold - Possible
Run on low oil - Possible

A combination of the possibles and shitty luck. Lets hope we dont see any more. I would consider my 12c highish miles at 21k, and all good in my camp.
 

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Lack of oil would cause wear before breakage.
Most likely a factory defect in the cam follower.
Revving when cold equals lack of oil.
 
2012 MP4-12C
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Discussion Starter · #57 ·
Lack of oil would cause wear before breakage.
Most likely a factory defect in the cam follower.
Revving when cold equals lack of oil.
This guy gets the series of events.

Could be a batch of bad followers.... but at riccardo they are spot on so unlikely
Something happening once in 10,000 engines still means it happened. It doesn't have to be likely to have happened.
 
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